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Mid-Latitude Cyclones
Mid-Latitude Cyclones
A mid-latitude cyclone is a large weather system that forms in the middle latitudes of Earth, roughly between 30° and 60° north or south of the equator. These storms are very common in places like the United States. They typically move from west to east across the country, often lasting several days and covering hundreds to thousands of miles. Mid-latitude cyclones are the major weather producers in the United States, and are responsible for much of the day-to-day weather we experience.
How Mid-Latitude Cyclones Form
How Mid-Latitude Cyclones Form
Mid-latitude cyclones form when warm tropical air and cold polar air collide. These storms are closely linked to fronts and the jet stream.
The process begins along a stationary front, where warm and cold air masses meet but neither is strong enough to move the other. A disturbance in the jet stream—often a wave or dip—causes air aloft to spread out (diverge). This removes air from above the surface, lowering surface air pressure and allowing a low-pressure system to form.
As surface pressure drops, warm air moves northward and cold air moves southward, creating a warm front in front and a cold front behind. The warm air rises over the colder air, forming clouds and precipitation. Because of Earth’s rotation (the Coriolis effect), air spirals inward toward the low pressure, causing the system to rotate counterclockwise in the Northern Hemisphere (clockwise in the Southern Hemisphere).
Over time, the faster-moving cold front catches up to the warm front, forming an occluded front. At this point, the storm begins to lose its energy source—the temperature difference between warm and cold air—and the cyclone gradually weakens and dissipates.
Reading Weather Maps
Reading Weather Maps
The purple arrow above shows the movement of the mid-latitude cyclone towards the NE.
Detroit: Falling air pressure because the Low (L) pressure center is getting closer to the city, cooler air temps because of the cP air mass, nimbostratus clouds with light to moderate precipitation. Light winds from the E.
Evansville: Falling air pressure because the Low (L) pressure center is getting closer to the city, warmer air temps because of the mT air mass, breezy SW winds. Few clouds and no precipitation yet, but possible cumulonimbus clouds and thunderstorms on the way.
Springfield: Low air pressure because the Low (L) pressure center nearby, warmer air temps because of the mT air mass, cumulonimbus clouds with thunderstorms. Breezy SW winds.
Highlighted in yellow above is a mid-latitude cyclone. Notice the Low (L) pressure center, the warm front in front and the cold front behind.
A: In front of the warm front - cooler air temps, light to moderate precipitation, most likely nimbostratus clouds, strong SE winds.
B: In front of the cold front - warmer air temps, heavy rains-possible thunderstorms or severe weather, most likely cumulonimbus clouds, calmer SW winds.
C: Near a High (H) pressure center (anticyclone), cooler air temps, clear skies, light W or NW winds.
D: Behind the cold front - colder air temps, less humidity, clearer skies, calm NW winds.
E: In front of the occluded front - cooler air temps, varied precipitation (light to moderate or possible thunderstorms or severe weather), strong NE winds.
Quizlet
📝QUIZ: Mid-Latitude Cyclones
🔄RETAKE QUIZ: Mid-Latitude Cyclones
📝QUIZ: Reading Weather Maps
🔄RETAKE QUIZ: Reading Weather Maps
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